The present disclosure relates to a time-to-digital converter and to a time-to-digital conversion method.
A time-to-digital converter (TDC) is a device used to measure a time interval and convert it into digital output. It allows measurements of very short times at high resolution. A problem with time-to-digital converters is the asynchronous nature of the physical effects that are measured. Each measurement has to be collected for further processing.
A time-to-digital converter is used in time-of-flight cameras, for example, to measure the time an emitted light signal like a laser pulse needs to travel to a reflecting object and back to the camera. A major drawback is that the average distance to all objects in a scene is only detected as a single number.
A well-known technique to implement a TDC uses a ring oscillator and a counter that is being driven by this ring oscillator, in particular by a clock edge progressing through the ring oscillator. A downside of this design is that by the time that the counter is being updated on the output, said edge has already progressed, so there is an inherent uncertainty for a counter value of the counter.